1. Technical Field
The present disclosure generally relates to a process cartridge and an image forming apparatus having a process cartridge.
2. Background
Using a process cartridge in an image forming apparatus is publicly known.
Such image forming apparatus may be an electro-photo copying machine, a printer, a facsimile, or a multi-functional machine capable of copying, printing, and facsimile.
The image forming apparatus includes a rotatable unit such as developing unit and cleaning unit, for example.
Such rotatable unit includes a rotating member such as developing roller and cleaning brush, for example. The rotating member has a shaft which is rotatably supported by the rotatable unit, and faces an image carrying member.
The above-mentioned process cartridge may have a configuration as explained below, for example.
A rotating gear is fixed on a shaft of the rotating member, and at least one idler gear is fixed on an idler shaft, which is rotatably supported by an unit body.
The rotating gear is meshed with the idler gear, and the idler gear is meshed with a main gear, which is rotatably supported by a frame of an image forming apparatus.
Therefore, rotation of the main gear can be transmitted to the rotating gear via the idler gear. Thereby, such configuration can drive the rotating member.
At this time, the pitch circle of the main gear and the pitch circle of the idler gear form a common tangent.
When the main gear rotates, in a line of action deviated from the common tangent with a pressure angle, the main gear applies an external force to the idler gear.
Therefore, the idler shaft is deformed periodically and vibrates. Such vibration of the idler shaft may be transmitted to the image carrying member. Thereby a banding action may happen on toner images formed on the image carrying member, and may result in image quality degradation.
Recently, an image forming apparatus using electro-photocopying process such as laser printer and digitally-controlled copying machine includes a process cartridge detachably provided to the image forming apparatus.
Such process cartridge includes a photoconductive member unit supporting a photoconductive member and at least one unit used for electro-photocopying process.
Such unit includes a developing unit, which develops an electrostatic latent image on the photoconductive member with toners, and a cleaning unit, which removes and recover toners remaining on the photoconductive member, for example.
Such developing unit and cleaning unit may be driven by a driving force transmitted from a driving source in the image forming apparatus.
Such developing unit and cleaning unit are referred as driven units because a driving force is transmitted from the driving source in the image forming apparatus. In this case, the photoconductive member unit is not referred as the driven unit.
A driving force is transmitted from the driving source in the image farming apparatus by coupling a driving gear of the image forming apparatus to a driven gear of each unit.
The process cartridge can be positioned in the image forming apparatus by placing a supported portion, provided to the photoconductive member unit, to a supporting portion, provided to the image forming apparatus.
In such configuration, the photoconductive member can be positioned in the image forming apparatus with higher precision, thereby the transfer of toner images from the photoconductive member to a transfer member can be favorably conducted.
However, in such positioning configuration, the driven unit such as developing unit and cleaning unit is attached to the image forming apparatus via the photoconductive member unit.
Therefore, if tolerances or manufacturing errors are accumulated up to a certain level, positional accuracy of such driven unit in the image forming apparatus may become deteriorated.
If the positional accuracy may deteriorate, a gear-to-gear distance between the driving gear and the driven gear may become larger or smaller from a predetermined distance, thereby engagement of the teeth of the gears may deteriorate.
If such drawback occurs, an unevenness in the a driving force transmission may results, thereby causing the driven gear to unevenly rotate, and vibration thereof may occur or the like, which leads to image quality degradation.
One background art device conducts positioning of a process cartridge and a driving system of an image forming apparatus using main reference and sub reference so that the image forming apparatus can correctly transmit a driving force to the process cartridge.
Another background art device uses technology which can maintain a distance between a photoconductive member and an developer carrying member by providing a slot hole for a supporting point of a driven unit in a direction perpendicular to a tangential direction of teeth engagement of a driving gear and a driven gear.
Still another background art uses a technology which can position a center of a photoconductive drum (i.e., photoconductive member) and a center of a developing sleeve with a predetermined positional relationship each other, and fix a photoconductive member case and developing member case with screws so that the photoconductive drum (i.e., photoconductive member) and the developing sleeve can be attached to an image forming apparatus with a higher precision.
However, such background devices may not cope with the above-mentioned drawbacks.